Changes in Sheep Oesophageal Diameter and Function during Geigeria Ornativa (vermeerbos) Poisoning and Subsequent Recovery

a INTRODUCTION Geigeria ornativa poisoning induces vermeersiekte, one of the most important plant poisonings of sheep on the subcon-tinent 2. It is characterised by regurgitation of ruminal contents through the mouth and nose, as well as stiffness, paresis and paralysis 3. At necropsy dilatation of the oesophagus is sometimes evident


INTRODUCTION
Geigeria ornativa poisoning induces vermeersiekte, one of the most important plant poisonings of sheep on the subcontinent 2 .It is characterised by regurgitation of ruminal contents through the mouth and nose, as well as stiffness, paresis and paralysis 3 .At necropsy dilatation of the oesophagus is sometimes evident 3 .The prognosis of vermeersiekte is usually good if stock is promptly removed from the toxic grazing 1,3 .However, Van Heerden, Van der Lugt & Durante (1993) 7 reported that mild dilatation of the oesophagus was still radiographically evident 55 days after intake of G. ornativa.This may have an impairing effect on the oesophageal function, resulting in decreased feed intake and production.Changes in the oesophageal diameter and function during and following clinical and subclinical intoxication with G. ornativa were investigated in case studies with sheep.

METHODS AND RESULTS
The effect of different doses of G. ornativa on the oesophageal diameter and function, body weight (BW), feed intake and the cardiopulmonary flow index (CPFI) for measuring cardiac function 6 was studied in 7 adult sheep.Sheep were presented with 20-100 g milled G. ornativa mixed with 100 g maize meal and 200 g milled lucerne each morning.They additionally received milled Eragrostis curvula hay ad lib.daily after the G. ornativa mixture had been ingested, which took between 1 and 2 hours to consume.Remains of the previous day's Eragrostis curvula hay were weighed before feeding.
Body weight was determined weekly in the morning after sheep had been fasted overnight.
The oesophageal diameter, expressed in terms of the oesophageal diameter index (ODI) (oesophageal diameter as a ratio of the length of the 7th thoracic vertebral body, illustrated in Fig. 1) 4 , was measured by survey radiography at maximal width.This was measured prior to any positive contrast medium administration and could only be done when there was luminal oesophageal gas present, which was the case in most of the affected animals.Oesophageal function (OF) was measured with fluoroscopy by following a swallowed bolus of milled feed mixed with barium contrast medium 4 .If a feed bolus passed directly through the cardiac sphincter into the reticulorumen, the OF was regarded as normal and quantified as 100 % functional.If the bolus did not pass directly into the reticulorumen, but lingered for a short time until a secondary or tertiary peristaltic wave allowed it to

ABSTRACT
Changes in the oesophageal diameter and function together with changes in body weight, feed intake and the cardiac pulmonary flow index were investigated during experimentally induced poisoning with Geigeria ornativa and subsequent recovery.This was performed under varying conditions for individual sheep.Results showed an increase in the oesophageal diameter index (ODI) during vermeersiekte, accompanied with a decrease in oesophageal function (OF).Cessation of G. ornativa intake resulted in a considerable although incomplete recovery of the ODI.Recovery of the OF for the different sheep, however, varied between 0 and 100 %.Detrimental changes in the oesophageal diameter and function were also measured in sheep receiving only subclinical doses of G. ornativa.Decreases in body weight and feed intake commenced 1 to 3 weeks before the onset of vermeersiekte, while indications of a decline in these 2 parameters were also noticed with ingestion of subclinical amounts of G. ornativa.An increase in the cardiac pulmonary flow index (CPFI) to a value indicating the onset of heart failure was found in 1 of the sheep showing clinical signs of vermeersiekte.The CPFI returned to normal after termination of G. ornativa intake.move through, the OF was considered as moderately affected and arbitrarily quantified as 75 % functional.If feed was partially retained in the thoracic oesophagus, the OF was described as severely affected and arbitrarily quantified as 50 % functional.If the swallowed feed accumulated in the thoracic oesophagus, as illustrated in Fig. 2, and did not move aborally at all during the examination time of a few minutes, the OF was described as extremely affected and arbitrarily quantified as 25 % functional (the OF was not quantified as 0 % since these sheep still managed to eat the forage presented to them).
The CPFI was obtained by measuring the number of heart beats necessary to pump radioactive technetium ( 99m Tc pertechnetate) in the blood from the heart to the lungs and back 6 .
Values for the different parameters, expressed as percentage of the maximum value, were graphically presented for each sheep.
Sheep 1, a Dorper wether, was fed G. ornativa collected in the Griekwastad (28°51'10''S, 23°14'54''E) district, Northern Cape.The dried plant material, mainly leafy, was fed for 42 days at a dose of 3.2 g/kg BW/day.The effect of G. ornativa during feeding and following its withdrawal on the different parameters until Day 202 is shown in Fig. 3

OBSERVATIONS AND CONCLUSIONS
The following observations were made from the results of this investigation: • Clinical signs of vermeersiekte developed after 21 to 28 days of G. ornativa intake at doses of 2 and 3.2 g/kg BW/day (Sheep 1 and 2, Figs 3 and 4a).A 5-day cessation of G. ornativa intake resulted in clinical recovery from vermeersiekte (Sheep 1 and 2; Figs 3, 4a and 4b).G. ornativa then had to be ingested for another 27 days (a lower dose) before clinical signs of vermeersiekte could be re-induced (Sheep 2, Fig. 4b).Vermeersiekte, however, could not be induced when G. ornativa was fed at levels varying between 30 % and 70 % of the corresponding toxic doses (Sheep 3, 4 and 5, tiva intake was followed shortly by an increase in body weight and feed intake (Figs 3, 4a and 4b).A considerable, although incomplete, recovery of the oesophageal diameter occurred (normal ODI values c. 0.1) after cessation of G. ornativa intake (Fig. 8a).Recovery was characterised by an initial rapid recovery that slowed down with time.
Recovery of the oesophageal function varied from full to no recovery at all (Fig. 8b).The increased CPFI during vermeersiekte returned to normal within 17 days after withdrawal from G. ornativa, indicating that the decrease in cardiac function was a reversible process that normalised quite rapidly.• These observations might be of great significance for optimal flock management on G. ornativa infested veld and therefore need to be confirmed in a well designed study.
. Recovery of the oesophageal diameter and function after withdrawal from G. ornativa until Day 776 is shown in Figs 8a and 8b respectively.The sheep revealed clinical signs of stiffness and paresis from Day 27 to Day 49.The oesophageal diameter index increased exceptionally during the occurrence of vermeersiekte, accompanied by c. 50 % decrease in oesophageal function.Body weight and feed intake were also adversely affected.Except for the oesophageal function, recovery of these parameters commenced soon after cessation of G. ornativa intake.Incomplete recovery of the oesophageal diameter index, with no recovery of the oesophageal function, was measured over a period of 776 days following cessation of vermeerbos intake.Sheep 2, a Merino wether, was fed with the same G. ornativa as Sheep 1, but at a dose of 2 g/kg BW/day for 25 days.Values for the different parameters measured until Day 79 are given in Fig. 4a.Signs of pronounced stiffness, paresis, and a green staining around the nose (indicating some regurgitation of rumen contents) became evident from Day 21 to 32.In addition to detrimental changes of the oesophageal diameter index and function, hay intake and body weight, the cardiac pulmonary flow index increased to a

Fig. 5 :
Fig. 5: Changes in some clinical and physiological parameters of Sheep 3 during poisoning with Geigeria ornativa.